When a shock is applied externally to the side of the vehicle due to a side impact or the like, the vehicle door or the vehicle structure may be deformed by the impact force depending on the magnitude of the shock. In order to relax the shock force to the passenger due to the deformation, various types of air bag are proposed which are inflated between the lateral face and the passenger when a side impact occurs, so that the shock force exerted on the passenger is absorbed by the air bag (e.g. Japanese Patent Laid-open Publication (OPI) 4-50052, Japanese OPI 4-356246, and so on).
A heretofore proposed side impact air bag system has an air bag folded up together with a gas generating device, both installed inside a vehicle seat (mainly in the seat back) to maintain the relative position to the passenger in a constant value, and is provided with detection means for detecting a side impact to blow the gas from the gas generating device. When a side impact is detected by the detection means, a gas is momentarily blown out from the gas generating device into the air bag to inflate the air bag towards the front side of the vehicle so that the air bag lies between the side of the vehicle and the passenger. By the air bag lying between the side of the vehicle and the passenger in the vehicle compartment, a shock to the passenger by a deformed door and the like is absorbed to protect the passenger.
In the conventional side impact air bag system, since the bag inflation direction is almost perpendicular to the input at collision, it is necessary to inflate the air bag momentarily by a high pressure in order to positively inflate in a narrow space between the vehicle body and the passenger. However, the part opposing the chest portion and the part opposing the abdomen portion of the passenger are inflated with almost the same width, the abdomen portion and the chest portion are applied with a same pressure when the bag is inflated, the shock to the chest portion is relatively high, and a desired shock absorption is not achieved.
With a view to eliminate the above prior art problems, a primary object of the present invention is to provide a side impact air bag system which can be positively inflated in a narrow space between the vehicle body and the passenger.
Another object of the present invention is to provide a side impact air bag system which is improved in restraining of the passenger.